Curtis, the only GOP candidate in the race not to vote for President Trump in the November 2016 election, topped former state lawmaker Chris Herrod by nearly 12 percent and lawyer Tanner Ainge by about 15 percent, according to preliminary election results.

During the GOP primary for Utah's 3rd congressional district, Curtis faced hundreds of thousands of dollars in attack ads run by out-of-state groups that sought to cast him as weak on benchmark conservative issues like lowering taxes.

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His victory on Tuesday sets him up for a clear victory in the state's special election in November. Democrats are not expected to heavily contest the district, where Republicans outnumber Democrats 5-1, according to The Associated Press.